Messages in this thread | | | Date | Thu, 22 Apr 2021 11:39:02 +0300 | From | Eli Cohen <> | Subject | Re: [PATCH] vdpa/mlx5: Add support for doorbell bypassing |
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On Thu, Apr 22, 2021 at 04:21:45PM +0800, Jason Wang wrote: > > 在 2021/4/22 下午4:07, Eli Cohen 写道: > > On Thu, Apr 22, 2021 at 09:03:58AM +0300, Eli Cohen wrote: > > > On Thu, Apr 22, 2021 at 10:37:38AM +0800, Jason Wang wrote: > > > > 在 2021/4/21 下午6:41, Eli Cohen 写道: > > > > > Implement mlx5_get_vq_notification() to return the doorbell address. > > > > > Size is set to one system page as required. > > > > > > > > > > Signed-off-by: Eli Cohen <elic@nvidia.com> > > > > > --- > > > > > drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 + > > > > > drivers/vdpa/mlx5/core/resources.c | 1 + > > > > > drivers/vdpa/mlx5/net/mlx5_vnet.c | 6 ++++++ > > > > > 3 files changed, 8 insertions(+) > > > > > > > > > > diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h b/drivers/vdpa/mlx5/core/mlx5_vdpa.h > > > > > index b6cc53ba980c..49de62cda598 100644 > > > > > --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h > > > > > +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h > > > > > @@ -41,6 +41,7 @@ struct mlx5_vdpa_resources { > > > > > u32 pdn; > > > > > struct mlx5_uars_page *uar; > > > > > void __iomem *kick_addr; > > > > > + u64 phys_kick_addr; > > > > > u16 uid; > > > > > u32 null_mkey; > > > > > bool valid; > > > > > diff --git a/drivers/vdpa/mlx5/core/resources.c b/drivers/vdpa/mlx5/core/resources.c > > > > > index 6521cbd0f5c2..665f8fc1710f 100644 > > > > > --- a/drivers/vdpa/mlx5/core/resources.c > > > > > +++ b/drivers/vdpa/mlx5/core/resources.c > > > > > @@ -247,6 +247,7 @@ int mlx5_vdpa_alloc_resources(struct mlx5_vdpa_dev *mvdev) > > > > > goto err_key; > > > > > kick_addr = mdev->bar_addr + offset; > > > > > + res->phys_kick_addr = kick_addr; > > > > > res->kick_addr = ioremap(kick_addr, PAGE_SIZE); > > > > > if (!res->kick_addr) { > > > > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > index 10c5fef3c020..680751074d2a 100644 > > > > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > @@ -1865,8 +1865,14 @@ static void mlx5_vdpa_free(struct vdpa_device *vdev) > > > > > static struct vdpa_notification_area mlx5_get_vq_notification(struct vdpa_device *vdev, u16 idx) > > > > > { > > > > > + struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev); > > > > > struct vdpa_notification_area ret = {}; > > > > > + struct mlx5_vdpa_net *ndev; > > > > > + > > > > > + ndev = to_mlx5_vdpa_ndev(mvdev); > > > > > + ret.addr = (phys_addr_t)ndev->mvdev.res.phys_kick_addr; > > > > > + ret.size = PAGE_SIZE; > > > > > > > > Note that the page will be mapped in to guest, so it's only safe if the > > > > doorbeel exclusively own the page. This means if there're other registers in > > > > the page, we can not let the doorbell bypass to work. > > > > > > > > So this is suspicious at least in the case of subfunction where we calculate > > > > the bar length in mlx5_sf_dev_table_create() as: > > > > > > > > table->sf_bar_length = 1 << (MLX5_CAP_GEN(dev, log_min_sf_size) + 12); > > > > > > > > It looks to me this can only work for the arch with PAGE_SIZE = 4096, > > > > otherwise we can map more into the userspace(guest). > > > > > > > Correct, so I guess I should return here 4096. > > > I'm not quite sure but since the calculation of the sf_bar_length is doen > via a shift of 12, it might be correct. > > And please double check if the doorbell own the page exclusively.
I am checking if it is safe to map the any part of the SF's BAR to userspace without harming other functions. If this is true, I will check if I can return PAGE_SIZE without compromising security. I think we may need to extend struct vdpa_notification_area to contain another field offset which indicates the offset from addr where the actual doorbell resides. > > > > > > > > I also think that the check in vhost_vdpa_mmap() should verify that the > > > returned size is not smaller than PAGE_SIZE because the returned address > > Actually I think it's ok since you verify the size equals vma->vm_end - > > vma->vm_start which must be at least PAGE_SIZE. > > > Yes. > > Thanks > > > > > > > might just be aligned to PAGE_SIZE. I think this should be enoght but > > > maybe also use the same logic in vhost_vdpa_fault(). >
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